package com.lagou.edu.mvcframework.servlet;

import com.lagou.demo.service.IDemoService;
import com.lagou.edu.mvcframework.annotations.*;
import com.lagou.edu.mvcframework.pojo.Handler;
import com.lagou.edu.mvcframework.proxy.SecurityProxy;
import org.apache.commons.lang3.StringUtils;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.*;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class LgDispatcherServlet extends HttpServlet {


    private Properties properties = new Properties();

    private List<String> classNames = new ArrayList<>(); // 缓存扫描到的类的全限定类名

    // ioc容器
    private Map<String,Object> ioc = new HashMap<String,Object>();


    // handlerMapping
    //private Map<String,Method> handlerMapping = now HashMap<>(); // 存储url和Method之间的映射关系
    private List<Handler> handlerMapping = new ArrayList<>();


    @Override
    public void init(ServletConfig config) throws ServletException {
        // 1 加载配置文件 springmvc.properties
        String contextConfigLocation = config.getInitParameter("contextConfigLocation");
        doLoadConfig(contextConfigLocation);

        // 2 扫描相关的类，扫描注解
        doScan(properties.getProperty("scanPackage"));


        // 3 初始化bean对象（实现ioc容器，基于注解）
        doInstance();

        // 4 实现依赖注入
        doAutoWired();

        // 5 构造一个HandlerMapping处理器映射器，将配置好的url和Method建立映射关系
        initHandlerMapping();

        //do Security proxy
        //doSecurityProxy();

        System.out.println("lagou mvc 初始化完成....");

        // 等待请求进入，处理请求
    }

    /*
        构造一个HandlerMapping处理器映射器
        最关键的环节
        目的：将url和method建立关联
     */
    private void initHandlerMapping() {
        if(ioc.isEmpty()) {return;}

        for(Map.Entry<String,Object> entry: ioc.entrySet()) {
            // 获取ioc中当前遍历的对象的class类型
            Object obj = entry.getValue();
            Class<?> aClass = obj.getClass();
            if(!aClass.isAnnotationPresent(LagouController.class)) {continue;}
            String baseUrl = "";
            if(aClass.isAnnotationPresent(LagouRequestMapping.class)) {
                LagouRequestMapping annotation = aClass.getAnnotation(LagouRequestMapping.class);
                baseUrl = annotation.value(); // 等同于/demo
            }
            // 获取方法
            Method[] methods = aClass.getMethods();
            for (int i = 0; i < methods.length; i++) {
                Method method = methods[i];
                if(method.isAnnotationPresent(LagouRequestMapping.class)) {
                    // 如果标识，就处理
                    LagouRequestMapping annotation = method.getAnnotation(LagouRequestMapping.class);
                    String methodUrl = annotation.value();  // /query
                    String url = baseUrl + methodUrl;    // 计算出来的url /demo/query
                    // 把method所有信息及url封装为一个Handler
                    Handler handler = new Handler(entry.getValue(), method, Pattern.compile(url));
                    // 计算方法的参数位置信息  // query(HttpServletRequest request, HttpServletResponse response,String name)
                    Parameter[] parameters = method.getParameters();
                    for (int j = 0; j < parameters.length; j++) {
                        Parameter parameter = parameters[j];

                        if (parameter.getType() == HttpServletRequest.class || parameter.getType() == HttpServletResponse.class) {
                            // 如果是request和response对象，那么参数名称写HttpServletRequest和HttpServletResponse
                            handler.getParamIndexMapping().put(parameter.getType().getSimpleName(), j);
                        } else {
                            handler.getParamIndexMapping().put(parameter.getName(), j);  // <name,2>
                        }

                    }
                    // 建立url和method之间的映射关系（map缓存起来）
                    handlerMapping.add(handler);
                }

            }
        }
    }


    //scan method which has Security annotation, replace it to proxy object
    private void doSecurityProxy() {
        if(handlerMapping.isEmpty()) {
            return;
        }

        for (Handler handler : handlerMapping) {
            Object controller = handler.getController();
            Method method = handler.getMethod();
            try {
                if (controller.getClass().isAnnotationPresent(Security.class)
                        || method.isAnnotationPresent(Security.class)) {
                    SecurityProxy securityProxy = new SecurityProxy(controller);
                    Object proxyTarget = Proxy.newProxyInstance(controller.getClass().getClassLoader(), controller.getClass().getInterfaces(),
                            securityProxy);
                    Method[] methods = proxyTarget.getClass().getMethods();
                    Method targetMethod = proxyTarget.getClass().getDeclaredMethod(method.getName(), method.getParameterTypes());
                    handler.setController(proxyTarget);
                    handler.setMethod(targetMethod);
                }
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            }
        }
    }

    private void doControllerSecurityProxy() {
        if(ioc.isEmpty()) {return;}

        for(Map.Entry<String,Object> entry: ioc.entrySet()) {
            Object obj = entry.getValue();
            Class<?> aClass = obj.getClass();
            //
            if(!aClass.isAnnotationPresent(LagouController.class)) {
                continue;
            }
            Method[] methods = aClass.getMethods();
            for (int i = 0; i < methods.length; i++) {
                Method method = methods[i];
                if(method.isAnnotationPresent(Security.class)) {
                    SecurityProxy securityProxy = new SecurityProxy(obj);
                    Object proxyTarget = Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(),
                            securityProxy);
                    ioc.put(entry.getKey(), proxyTarget);
                    break;
                }
            }
        }
    }

    //  实现依赖注入
    private void doAutoWired() {
        if(ioc.isEmpty()) {return;}

        // 有对象，再进行依赖注入处理

        // 遍历ioc中所有对象，查看对象中的字段，是否有@LagouAutowired注解，如果有需要维护依赖注入关系
        for(Map.Entry<String,Object> entry: ioc.entrySet()) {
            // 获取bean对象中的字段信息
            Field[] declaredFields = entry.getValue().getClass().getDeclaredFields();
            // 遍历判断处理
            for (int i = 0; i < declaredFields.length; i++) {
                Field declaredField = declaredFields[i];   //  @LagouAutowired  private IDemoService demoService;
                if(!declaredField.isAnnotationPresent(LagouAutowired.class)) {
                    continue;
                }


                // 有该注解
                LagouAutowired annotation = declaredField.getAnnotation(LagouAutowired.class);
                String beanName = annotation.value();  // 需要注入的bean的id
                if("".equals(beanName.trim())) {
                    // 没有配置具体的bean id，那就需要根据当前字段类型注入（接口注入）  IDemoService
                    beanName = declaredField.getType().getName();
                }

                // 开启赋值
                declaredField.setAccessible(true);

                try {
                    declaredField.set(entry.getValue(),ioc.get(beanName));
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }

            }


        }
    }


    // ioc容器
    // 基于classNames缓存的类的全限定类名，以及反射技术，完成对象创建和管理
    private void doInstance()  {

        if(classNames.size() == 0) return;

        try{

            for (int i = 0; i < classNames.size(); i++) {
                String className =  classNames.get(i);  // com.lagou.demo.controller.DemoController

                // 反射
                Class<?> aClass = Class.forName(className);
                // 区分controller，区分service'
                if(aClass.isAnnotationPresent(LagouController.class)) {
                    // controller的id此处不做过多处理，不取value了，就拿类的首字母小写作为id，保存到ioc中
                    String simpleName = aClass.getSimpleName();// DemoController
                    String lowerFirstSimpleName = lowerFirst(simpleName); // demoController
                    Object o = aClass.newInstance();
                    ioc.put(lowerFirstSimpleName,o);
                }else if(aClass.isAnnotationPresent(LagouService.class)) {
                    LagouService annotation = aClass.getAnnotation(LagouService.class);
                    //获取注解value值
                    String beanName = annotation.value();

                    // 如果指定了id，就以指定的为准
                    if(!"".equals(beanName.trim())) {
                        Object o = aClass.newInstance();
                        ioc.put(beanName,o);
                    }else{
                        // 如果没有指定，就以类名首字母小写
                        beanName = lowerFirst(aClass.getSimpleName());
                        Object o = aClass.newInstance();
                        ioc.put(beanName,o);
                    }
                    // service层往往是有接口的，面向接口开发，此时再以接口名为id，放入一份对象到ioc中，便于后期根据接口类型注入
                    Class<?>[] interfaces = aClass.getInterfaces();
                    for (int j = 0; j < interfaces.length; j++) {
                        Class<?> anInterface = interfaces[j];
                        // 以接口的全限定类名作为id放入
                        Object o = aClass.newInstance();
                        ioc.put(anInterface.getName(),o);
                    }
                }else{
                    continue;
                }

            }
        }catch (Exception e) {
            e.printStackTrace();
        }
    }


    // 首字母小写方法
    public String lowerFirst(String str) {
        char[] chars = str.toCharArray();
        if('A' <= chars[0] && chars[0] <= 'Z') {
            chars[0] += 32;
        }
        return String.valueOf(chars);
    }




    // 扫描类
    // scanPackage: com.lagou.demo  package---->  磁盘上的文件夹（File）  com/lagou/demo
    private void doScan(String scanPackage) {
        String scanPackagePath = Thread.currentThread().getContextClassLoader().getResource("").getPath() + scanPackage.replaceAll("\\.", "/");
        File pack = new File(scanPackagePath);

        File[] files = pack.listFiles();

        for(File file: files) {
            if(file.isDirectory()) { // 子package
                // 递归
                doScan(scanPackage + "." + file.getName());  // com.lagou.demo.controller
            }else if(file.getName().endsWith(".class")) {
                String className = scanPackage + "." + file.getName().replaceAll(".class", "");
                classNames.add(className);
            }
            
        }


    }

    // 加载配置文件
    private void doLoadConfig(String contextConfigLocation) {

        InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);

        try {
            properties.load(resourceAsStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }


    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 处理请求：根据url，找到对应的Method方法，进行调用
        // 获取uri
//        String requestURI = req.getRequestURI();
//        Method method = handlerMapping.get(requestURI);// 获取到一个反射的方法
        // 反射调用，需要传入对象，需要传入参数，此处无法完成调用，没有把对象缓存起来，也没有参数！！！！改造initHandlerMapping();
//        method.invoke() //


        // 根据uri获取到能够处理当前请求的hanlder（从handlermapping中（list））
        Handler handler = getHandler(req);

        if(handler == null) {
            resp.getWriter().write("404 not found");
            return;
        }

        // 参数绑定
        // 获取所有参数类型数组，这个数组的长度就是我们最后要传入的args数组的长度
        Class<?>[] parameterTypes = handler.getMethod().getParameterTypes();


        // 根据上述数组长度创建一个新的数组（参数数组，是要传入反射调用的）
        Object[] paraValues = new Object[parameterTypes.length];

        // 以下就是为了向参数数组中塞值，而且还得保证参数的顺序和方法中形参顺序一致

        Map<String, String[]> parameterMap = req.getParameterMap();

        String name = "";
        // 遍历request中所有参数  （填充除了request，response之外的参数）
        for(Map.Entry<String,String[]> param: parameterMap.entrySet()) {
            // name=1&name=2   name [1,2]
            String value = StringUtils.join(param.getValue(), ",");  // 如同 1,2

            // 如果参数和方法中的参数匹配上了，填充数据
            if(!handler.getParamIndexMapping().containsKey(param.getKey())) {continue;}

            // 方法形参确实有该参数，找到它的索引位置，对应的把参数值放入paraValues
            Integer index = handler.getParamIndexMapping().get(param.getKey());//name在第 2 个位置

            paraValues[index] = value;  // 把前台传递过来的参数值填充到对应的位置去

            if ("name".equals(param.getKey())) {
                name = value;
            }

        }


        int requestIndex = handler.getParamIndexMapping().get(HttpServletRequest.class.getSimpleName()); // 0
        paraValues[requestIndex] = req;


        int responseIndex = handler.getParamIndexMapping().get(HttpServletResponse.class.getSimpleName()); // 1
        paraValues[responseIndex] = resp;

        if (!doCheckSecurity(handler.getController(), handler.getMethod(), name)) {
            resp.getWriter().write("user: [" + name + "] is forbidden!");
            return;
        }

        // 最终调用handler的method属性
        try {
            handler.getMethod().invoke(handler.getController(),paraValues);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    private boolean doCheckSecurity(Object controller, Method method, String name) {
        //check method's security annotation
        if (method.isAnnotationPresent(Security.class)) {
            Security annotation = method.getAnnotation(Security.class);
            String[] userNames = annotation.value();
            for(String userName : userNames) {
                if (name.equals(userName)) {
                    return true;
                }
            }
            System.out.println(name + " is not in whitelist, forbidden!");
            return false;
        } else {
            //if method has no security annotion, user controller's
            if (controller.getClass().isAnnotationPresent(Security.class)) {
                Security objAnnotation = controller.getClass().getAnnotation(Security.class);
                String[] userNames = objAnnotation.value();
                for(String userName : userNames) {
                    if (name.equals(userName)) {
                        return true;
                    }
                }
            }
            return true;
        }
    }

    private Handler getHandler(HttpServletRequest req) {
        if(handlerMapping.isEmpty()){return null;}

        String url = req.getRequestURI();

        for(Handler handler: handlerMapping) {
            Matcher matcher = handler.getPattern().matcher(url);
            if(!matcher.matches()){continue;}
            return handler;
        }

        return null;

    }


}
